Expanding reamer



June 13, 1950 E. s. ROBINSON 2,511,650

EXPANDING REAMER Filed Oct. 22, 1948 351E213 Efiua- W was H ATTORNEYSPatented June 13, 1950 UNITED STATES PATENT OFFICE EXPANDING REAMERErnest 8. Robinson, Brentwood, Md. Application October 22, 1948, SerialNo. 55,929

2 Claims. 1

This invention relates to reamers and has more particular reference toreamers adapted to form undercut openings in the bottom of holes.

One object of the invention is to provide a reamer having one or morepivoted cutters adapted to be swung outwardly by a wedge member to forma irusto-conical undercut at the bottom of a hole.

Another object of the invention is to provide a reamer, as abovecharacterized, wherein the body of the reamer is hollowed to form ahousing for the wedge member.

Another object of the invention is to provide a reamer, as abovecharacterized, wherein the cutters are readily removable for sharpeningor replacement.

Another object of the invention is to provide a reamer, as abovecharacterized, wherein the wedge member is normally held in a protractedposition by resilient means.

A further object of the invention is to provide a reamer, as abovecharacterized, which is simple and rugged in construction, economical inmanufacture and eiiicient in operation.

Other objects and advantages oi the invention will appear in thefollowing specification when considered in connection with theaccompanying drawing, wherein:

Fig. 1 is a front elevational view of a reamer constructed in accordancewith the present invention;

Fig. 2 is a side elevational view with parts broken away, of the reamershown in Fig. 1, and showing the manner in which it is operated:

Fig. 3 is a partial side elevational view, similar to Fig. 2, with partsbroken away, and showing the wedge member in protracted position; and

Fig. 4 is an enlarged horizontal sectional view taken on the line l4 ofFig. 1.

Referring now to the several figures hi the drawing, there is shown areamer comprising a mandril It provided with a central chamber I I,which extends longitudinally thereof, a slidable wedge member l2, and acoiled spring I! mounted in the chamber, and a pair of cutters II, IIpivotaily mounted on the mandril adjacent the open end of the chamber.

The lower portion of the mandril III is provided with an oppositelydisposed pair of slots II, I I, in

which the cutter members ll, II are pivotally mounted on pins II, Itextending across the respective slots It, I I. The upper end of themandril is provided with a squared shoulder or head 2| adapted to engagethe socket of any ordinary bit stock or similar boring device.

The wedge member it comprise a cylindrical stem 2! having a piston-likeshoulder 22 formed on its upper end and a trusto-conical shoulder 23formed on its lower end. The upper shoulder 22 is of less diameter thanthe internal diameter of the cylindrical chamber l I to permit the wedgemember to freely slide therein. The frusto-conical shoulder 21 forms thewedge for engaging the inner edges of the cutters to force themoutwardly.

The cutter member I is generally rectangular in outline and crosssection. Its outer side wall is cut away to form a longitudinallyextending cutting edge 24 and its inner side wall is provided with alongitudinally extending rounded groove 25 which normally engages thestem II of the wedge member. The cutter member Ills similar inconstruction to the cutter member I 4 and has an outer longitudinallyextending cutting edge It and a longitudinally extending rounded groove21 formed on its inner wall.

The bottom edges or walls of the two cutter members I4, I! are tapereddownwardly and outwardly, as indicated at 28, 29, respectively, so thatwhen the bottoms oi the cutter members engage the bottom of the holewhich is being undercut, they will lie flat on the bottom of the hole,as shown in Fig. 2.

The normal position of the cutters and the wedge member is shown in Fig.3. As there shown. the cutters are housed in their respective slots withtheir cutting edges even with the edges of the slot. The wedge member isprotracted by the spring with the bottom edge of the upper shoulder 22resting on the inner upper edges of the cutter members. In this positionthe spring II is not tensioned.

The coiled spring II is loosely mounted in the upper end of the chamberII with its top end engaging the top of the chamber and with its bottomend engaging the top end of the shoulder 22 of the wedge member I2. Thespring normally holds the wedge member in a protracted position with thebottom edge oi the shoulder 22 engaging the top inneredges of the cuttermembers.

It will be noted that the cutter members extend well below the bottom oithe mandril (see Figs. 1, 2 and 3). This allows the shavings or chipscreated by the reaming process to collect between the exposed ends ofthe cutter members at the bottom of the hole. In addition, a pair ofelongated rounded recesses 30, ll are formed on the outer surface of themandril, each posi- 3 tioned circumferentially in front of the cuttingedges of the cutter members.

The manner in which the reamer is operated is believed to be obvious. Itis inserted in a prebored hole in a piece of wood or other suitablematerial, the hole being of slightly larger diameter than the diameterof the reamer, until the bottom of the wedge member rests in the bottomof the hole. As pressure is applied on the mandril with the reamerrotating, the cutter members will be forced increasingly outward to forma frusto-conical undercut extending upwardly from the bottom of thehole. This is illustrated in Fig. 2, where there is shown in crosssection a block of wood 32 having three semi-cylindrical holes I3, 34and 35 formed therein. The hole 33 has not been undercut, the hole 34has been undercut, while the reamer is shown (partly in cross section)in hole 35 completing an undercut therein.

From the foregoing, it readily will be seen that there has been provideda reamer for forming undercuts in the bottom of holes which is simpleand rugged in construction, economical in manufacture, and eflicient inoperation, and having cut-' ters which may readily be removed forsharpening or replacement.

What is claimed is:

1. An expanding reamer for forming a frustoconical undercut at thebottom of a bored hole comprising a cylindrical mandrel adapted to beinserted in the hole and having a cylindrical axial bore extendingthrough its lower end, and terminating short of its upper end; the lowerend por- 4' tion of the mandrel having longitudinally extending andcircumferentially spaced, radial slots; longitudinally extendingcuttingblades pivotally mounted at their upper.ends in said slots andprojecting below the lower end of said mandrel with their upper innerend portions extending slightly into the bore; a frusto-conical wedgemember coacting with the inner edges of said blades and having a stemprojecting into said bore; a piston-like shoulder member on the upperend of said stem slidably mounted in said bore and confined therein bythe inwardly projecting upper ends of said blades; a compression coilspring loosely mounted in the bore and abutting the upper end of saidpiston-like shoulder normally projecting the frusto-conical wedge belowthe lower ends of said blades.

2. An expanding reamer, as set forth in claim 1,

wherein the mandrel has longitudinally extendins recesses in" its outerwall in front of the cutting edges of the blades to receive shavings.

ERI IEST S. ROBINSON.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 752,724 Taylor Feb, 23, 1904762,458 Willard June 14, 1904 833,240 Potter Oct. 16, 1906 2,214,484Seal Sept. 10, 1940 2,401,074 Huelster May 28, 1946

